The semiconductor industry has experienced rapid growth, and demands for highly integrated semiconductor devices are increasing. Technological advances in integrated circuit (IC) design and materials have produced generations of ICs. Each generation has smaller and more complex circuits than previous generations. In the course of IC evolution, functional density has generally increased while geometric size (i.e., the smallest component (or line) that can be created through a fabrication process) has decreased.
These demands for scaling down have increased the complexity of processing and manufacturing semiconductor devices for ICs. For example, as the critical dimension (CD) of features for ICs is scaled down, it may be difficult to form these features having the desired CD using conventional lithography processes because the wavelength of the light used in these lithography processes is reaching its technical limitations. For such demands to be met, similar developments in IC processing and manufacturing are needed.
Although existing methods for fabricating IC devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every respect. Improved techniques for multiple patterning may relax existing design rules, overcome existing limitations, and thereby enable even more robust circuit devices to be manufactured.